This invention relates broadly to the mining of minerals, and particularly to the mining of strata bound deposits such as gold, uranium and coal, and non-stratiform deposits. The scope of the invention is however not limited to these named applications.
In all mining situations the ore-bearing zones vary both quantitatively and qualitatively. The ability to mine a particular ore therefore depends on precise knowledge of the characteristics of the rock at a given working face. This information permits the selection of economic mining horizons and enables the grade of ore mined and the production rate to be controlled. Intimately associated with these objectives are the monitoring of foot wall and hanging wall conditions and the negotiation of structural discontinuities.
At present a mine is planned on data collected from exploration drill holes. As surface drilling is expensive the drill holes are widely spaced and can therefore only indicate the general nature of the ore body. More pertinent data is therefore collected during mining operations at the face. The present precedure for quality control involves the manual collection of samples at the working face at regular intervals. The samples are analysed and the mining thereafter proceeds on the analyses and predictions arising therefrom and on the other data which is normally employed. The problem with this technique however is that the analysis is dependent on the properties of the mining face itself, where mining is actually taking place, and that account is not taken of the properties of the rock remote from the face; thus the mining proceeds and is corrected when the interpreted results are available.
Each mine has its own particular problems. For example in tin mining the pay zones are frequently irregularly distributed. In many sulphide deposits the economic limit may be expressed as a function of various contributing metals. In multi-seam and multi-product coal mines the positions, grades and dimensions of the various seams must frequently be monitored.
When test boreholes are drilled from surface it is commonplace to make use of wire line logs for continuously sampling the boreholes. Such devices are however not suitable for underground use where the test drilling may take place in all directions including the vertical upward direction.
U.S. Pat. No. 3,015,477 proposes a coal-rock sensing device which employs test probes adjacent the cutting bits of a coal mining machine. The technique enables the machine to be kept "on course" but in other respects it is only of limited value.